Study looks at Antarctic sea ice changes since the early 20th century, increases since 1979

Antarctica

The article says ‘The satellite measurements start in 1979’, but the USGS Landsat satellite project has been ‘imaging the Earth since 1972’. The researchers say in the abstract of their paper: ‘In stark contrast to the Arctic, there have been statistically significant positive trends in total Antarctic sea ice extent since 1979. However, the short and highly variable nature of observed Antarctic sea ice extent limits the ability to fully understand the historical context of these recent changes.’ The UK Met Office reported in October 2021: ‘Antarctic sea ice reached a maximum extent (to date) of 18.75 million sq km on 1st September 2021 (Figure 7), which is very close to the 1981-2010 average maximum extent of 18.70 million sq km.’
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A study led by Ohio University researchers shows that the increase of sea ice surrounding Antarctica since 1979 is a unique feature of Antarctic climate since 1905—an observation that paints a dramatic first-ever picture for weather and climate implications on the world’s southernmost continent, says Phys.org.

Dr. Ryan Fogt’s study, published today in Nature Climate Change, is the first to detail sea ice extent surrounding the entire continent though all four seasons over the last century.

Weather, especially winds and temperatures, contribute to sea ice changes. Fogt is professor of Geography in OHIO’s College of Arts and Sciences.

Previous historical estimates of Antarctic sea ice before satellite measurements began around 1979 were obtained mostly through the lens of a small number of weather stations across the vast continent, human observation along the ice edges, and ice core and ocean sediment samples.

However, these estimates all have limitations—most were only observing sea ice conditions in a small area or at a specific time of the year.

But the OHIO study extends the reliable measurements from satellite imagery since 1979 back through the 20th century using historical weather data at places away from the Antarctic continent.

At the heart of Fogt’s statistical reconstruction model is the strong connection Antarctic sea ice shares with regional and large-scale climate variability, captured through a network of 30 long-term temperature and pressure observations across the Southern Hemisphere.

This new study has nearly tripled the length of observed data about the entire continent, instead of just a specific region, and provides a year-round look, rather than an annual average.

“This reconstruction of Antarctic sea ice back through the 20th century gives us detail not only for every season, but also for different regions around the whole of Antarctica. When we sum it up, it gives us the first complete estimate of total Antarctic sea ice extent—how far away the sea ice reaches from the continent—back through the 20th century,” Fogt said.

Regime Shift: Sea increases since 1979, and sudden declines

From the new data, the most impressive feature is what Fogt calls a regime shift. “The short period provided from satellite measurements of Antarctic sea ice is really unique. It’s the only period since the beginning of the 20th century where we see increases in total sea ice in all seasons,” Fogt said.

“We have a statistically significant positive trend over that satellite period. Perhaps even more impressively, these increases since 1979 are juxtaposed by long-term decreases in Antarctic sea ice throughout the early and middle 20th century.”

Ice core records similarly confirm regional aspects of the decrease in much of the 20th century.

Full article here.